1. Field
The described technology relates generally to a display device, and more particularly, to a display device including a thin film transistor which uses an oxide semiconductor as an active layer.
2. Description of the Related Technology
A thin film transistor may be used as a pixel switching element of a flat panel display. An active layer of the thin film transistor may be mainly formed of amorphous silicon or polycrystalline silicon. The amorphous silicon active layer may be easily deposited on a large area and processed at a low temperature, but has a drawback of low charge mobility. The polycrystalline silicon active layer has excellent electrical characteristic due to high charge mobility, but demands a high temperature process and has difficulty in reliable uniformity.
A thin film transistor including an oxide semiconductor (for example, zinc oxide or gallium-indium-zinc oxide) as the active layer has both of an advantage of amorphous silicon capable of being processed at a low temperature and an advantage of polycrystalline silicon having high charge mobility. However, a component characteristic of the oxide semiconductor active layer may deteriorate by coming in contact with gas containing hydrogen that may be used in a subsequent passivation process.
Particularly, a passivation layer formed of a silicon nitride layer or a silicon oxide layer may be located on the thin film transistor. The passivation layer may be formed by CVD or PECVD, and during the process, gas, such as SiH4 and NH3, containing a large amount of hydrogen may be used. The hydrogen contained in the gas flows through the active layer, so that an initial characteristic and long-term reliability of the thin film transistor may deteriorate.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.